1. Field of the Invention
The present invention relates to a container for retort pouch food, more particularly to a container for retort pouch food which can be cooked in a microwave oven.
2. Description of the Related Art
The retort pouch food has a number of advantages. For example, the retort pouch food, which is hygienically sealed in an airtight container, and pressurized and heated to be sterilized, has a good keeping quality. Further, the retort pouch food is simply dipped in hot water to be heated when used, and therefore, can be easily cooked. Because of these advantages, the retort pouch food is made widely and often available.
When a microwave oven is used for heating, the retort pouch food can be more speedily cooked in an energy-saving manner. Therefore, the microwave oven is often used for heating a container for the retort pouch food.
The container for the retort pouch food usable in the microwave oven generally available is obtained in such a manner that a laminate film including resin superior in an oxygen blocking property such as vinylidene chloride is thermally adhered to an upper-surface opening of a main body of the container containing contents so that the contents can be sealed therein. Because the airtight container for retort pouch food bursts and the contents thereby pop out when heated, the container is previously provided with holes at a few sections thereof with a fork or the like before heating, or heated in several times. More specifically, in many cases, a top sealing sheet of the container (sealing part which is easily peelable) is peeled and the contents are stirred, and thereafter, the container is sealed with a cover film and heated, the container is removed from the microwave oven so that the contents in the container are stirred again, and the container is heated again in the microwave oven. The described process, in which it becomes necessary to form the holes in the container and stir the contents, and the contents may pop out of the container if the holes are not correctly made, was not favorable.
In order to make it unnecessary to form the holes, a container for retort pouch food which is heated in the microwave oven after a part of the sealing sheet of the container is peeled before heating was manufactured. An easy peeling process is applied to the container for retort pouch food in advance so that the particular part of the sealing sheet can be easily peeled. The easy peeling process adopts, for example, a method in which a slit is previously formed at an end of the laminate film thermally adhered to the container main body and the container is sealed with a specially-made ink also serving as an adhesive.
In the case of the foregoing method, however, the contents contained in the container main body, if they are liquid or gas exchange packaging, may unfavorably leak from the slit during the transportation to the consumers' market. Another disadvantage is that the easy peeling process inevitably increases a manufacturing cost of the container itself.